1. Field of the Invention
This invention relates in general to earth boring bits and in particular to improvements in those bits using earth removing teeth formed of hard metal inserts retained in mating holes by interference fit.
2. Description of the Prior Art
Sintered tungsten carbide is shaped to formed earth removing teeth that protrude from interferringly sized holes in steel rotatable cutters of earth boring bits. Similar inserts are used in rotary percussive bits that are struck repetitively by a motor driven hammer. In either type bit high level cyclic stress waves pass repeatedly through the inserts and their supporting metal. As a consequence, insert fractures and fatigue failures in the supporting metal have been problems that occasionally appear, especially when drilling conditions are severe.